We have demonstrated for the first time that synthetically modified actinomycin D (AMD) analogs (7-nitro AMD and 7-amino AMD) exhibit DNA- binding properties, DNA-guanine specificity, and inhibitory properties against mammalian cells in vitro and against four transplantable mouse tumors in vivo comparable to those of AMD itself. Despite the sensitivity of AMD to nearly all chemical manipulations and consequent loss of biological activity, it is now clear that biological specificity, including antitumor properties, can be retained in 7- substituted analogs. Furthermore, we have shown that the antibacterial activity of AMD analogs, long used to indicate biological usefulness of such compounds, does not provide reliable predictive data for other bioassay systems, particularly those involving mammalian cells. We now wish to extend our preliminary observations. We propose a combined chemical and pharmacological approach to the development of novel analogs of AMD with retention of DNA-binding specificity and, hopefully, with improved antitumor properties. We intend to introduce lipophilic, basic, and peptidic substitution at position 7 of AMD and to evaluate these analogs thoroughly in a number of in vitro and in vivo biological systems. DNA-binding and DNA-directed RNA polymerase inhibition measurements will be conducted. Since several of these analogs are expected to be fluorescent, cell localization and transport studies will be facilitated.